1. Field
Embodiments described herein related generally to a nuclear medical imaging apparatus, an image processing apparatus, and an image processing method.
2. Description of the Related Art
Conventionally, nuclear medical imaging apparatuses, such as a gamma camera, a Single Photon Emission (SPE) Computed Tomography (CT) apparatus (SPECT apparatus), and a Positron Emission CT apparatus (PET apparatus), are widely used in today's medical fields as a medical diagnostic imaging apparatus that can perform a functional diagnosis on living tissue of a subject.
A nuclear medical imaging apparatus measures from the outside of body a gamma ray emitted from an isotope or a labeled compound that is selectively captured into living tissue, and reconstructs a nuclear medical image that a radiation dose distribution of the measured gamma ray is imaged. For example, the nuclear medical imaging apparatus reconstructs a nuclear medical image on which a distribution of tumor tissue that captures an isotope or a labeled compound is rendered, thereby providing functional information about living tissue of a subject to a doctor who performs image diagnosis.
Recently, an apparatus into which a nuclear medical imaging apparatus and an X-ray Computed Tomography (CT) apparatus that images morphological information in living tissue of a subject are integrated (for example, a PET-CT apparatus or a SPECT-CT apparatus) is implemented in practice.
For example, a PET-CT apparatus can acquire a PET image reconstructed by a PET apparatus, and an X-ray CT image reconstructed by an X-ray CT apparatus with respect to the same cross section of a subject, and can simultaneously refer to functional information acquired from the PET image and morphological information acquired from X-ray CT image, thereby enabling a doctor to perform image diagnosis with high precision. Moreover, the PET-CT apparatus can create and display a composite image that a PET image and an X-ray CT image are combined.
Examinations by using a PET-CT apparatus or a SPECT-CT apparatus are generally performed on the same portion of the same subject a plurality of number of times (for example, before treatment and after treatment), and results of the examinations are presented by displaying in parallel layout nuclear medical images that are registered in accordance with X-ray CT images.
However, even if results of examinations before and after a treatment are displayed in parallel layout, it is difficult for a doctor to determine intuitively a detailed difference that is changed owing to the treatment, such as the size of a tumor.
Therefore, a technology has been known that a differential image is created by differentiating pixel values (Standard Uptake Value (SUV)) of corresponding pixels on nuclear medical images that are registered in accordance with X-ray CT images, and the created differential image is displayed as a result of a plurality of examinations. In other words, by referring to a differential image, a doctor can objectively determine, for example, a distributional change in tumor tissue that is changed between before and after a treatment.
However, information displayed on the above differential image is only differential information between nuclear medical images of respective examinations subjected to comparison; consequently, the doctor cannot grasp information about original values of respective nuclear medical images subjected to comparison, even by referring to the differential image. As well as differential information, for a doctor who performs image diagnosis, it is important to grasp from what value to what value an SUV value changes in order to determine a region to be focused on for planning courses for a treatment, for example, a region in which a treatment effect is large, a region in which a treatment effect is small, and a region into which a tumor metastasizes.
Although a differential image can be displayed in parallel layout together with a plurality of nuclear medical images subjected to comparison, a doctor performs image diagnosis by referring to three images, so that it is difficult to determine objectively a region to be focused on.
As described above, there is a problem that the above conventional technology does not necessarily assist image diagnosis by a doctor who compares a plurality of examination results.